This invention relates to a fluororesin composition useful as a pressure sensitive adhesive composition. Essentially the resin composition is a blend of a vinylidene fluoride base copolymer and an acrylate base copolymer.
Most of conventional pressure sensitive adhesives for adhesive tapes and sheets are essentially composed of an elastomeric polymer and a tackifier. The elastomeric polymer, which provides cohesive force, is selected from natural and synthetic rubbers, polyvinyl ether, polyvinyl acetate, polyacrylates, silicone resins, etc. Rubber base compositions have been long predominant, but in recent years acrylic resin base pressure sensitive adhesive compositions have achieved a remarkable development.
Acrylic polymers are superior to rubbers in weather resistance and oil resistance. Besides, acrylic monomers are high in copolymerizing capabilities so that it is easy to variously modify acrylic resins by copolymerization with consideration of variations in polarity of the surfaces to which the respective adhesives are to be applied.
However, thermoplastic acrylic polymers are generally low in intermolecular cohesive force and, therefore, are insufficient in creep resistance and heat resistance. A known technique to acquire an improved balance of tack adhesion strength and cohesive force is producing a copolymer comprising an acrylic ester segment relatively large in chain length and relatively low in glass transition temperature (T.sub.g) and another acrylic or methacrylic ester segment shorter in chain length and higher in T.sub.g. Besides such two components sometimes a polar vinylic monomer is copolymerized as a third component for further enhancement of the cohesive force. Also it is known to solve the problem of insufficient cohesive force by introducing reactive radicals into acrylic polymers to obtain cross-linkably modified acrylic resins.
Despite such efforts still it is difficult to afford sufficiently strong cohesive force to a pressure sensitive adhesive composition having good weatherability, heat resistance, water resistance and oil resistance. Besides, when a fluororesin is used as the base material of an adhesive tape there is a problem that few of conventional pressure sensitive adhesive compositions can well wet the tape base.